Method of making dry cells and batteries



March 1953 J. J. COLEMAN EIAL 2,632,783

" METHOD OF MAKING DRY CELLS AND BATTERIES Original Filed Dec. 16, 1948I 5/114 iii/11514,

INVENTORS. gofloflzam/ Patented Mar. 24, 1953 METHOD OF MAKING DRY CELLSAND BATTERIES Joseph J. Coleman and Milton E. Wilke, Freeport, Ill.,assignors to Burgess Battery Company, Freeport, 111., a corporation ofDelaware Original application December 16, 1948, Serial No. 65,591.Divided and this application October 24, 1950, Serial No. 191,782

6 Claims. 1 This invention relates to electric dry cells and batteries,and more particularly to an improved method of making the same. Thisapplication is a division of application Serial No. 65,591, filedDecember 16, 1948.

The electric output capacity f a dry cell and the ability of the cell todeliver a heavy sustained current depend, in part, upon the quantitiesof chemical reactants in the cell and the arrangement of the elements inthe cell structure. The eflicient use of space results in the productionof a cell having satisfactory electrical capacity when the participatingchemical substances are properly proportioned and the cell elements arearranged for proper access to each other with resulting eflicientinteraction.

Generally speaking, the current output of a cell of the'Le Clanche typemay be increased by increasing the area of the negative electrode whichis exposed to electrolytic action in the process of generatingelectricity. By so increasing the area of the negative electrode, thepolarization effect is diminished or retarded and the internalresistance of the cell reduced.

Referring to the flat type of cell in which the negative electrode isformed principally by a flat area, and the depolarizing mass or mix isin the shape of a flat slab or block, it has heretofore been proposed toemploy a flanged negative electrode member which covers more than oneflat surface of the mix block. Electrodes having a U shape wherein theportion connecting the two legs of the electrode forms the bottom of thecell have also been proposed and have been used. Other more complexelectrode structures which more or less completely enclose the mix blockhave been suggested. Where the simpler elements are employed in cellshaving terminals at the tops thereof for electrical connection to form abattery, the tops of the cells have been left open with the mix blockand portions of the negative electrode and separator exposed to becovered at a later stage in the production process by a sealingmaterial. This arrangement requires the observation of certaintolerances in the construction of the elements and theirarrangement inthe cell. Extra precautions must be taken to avoid the possibility ofthe short-circuiting of the cell by a mix crumb which makes contact withthe negative electrode above the separator.

The invention described in the copending application above referred toprovides a cell and battery of high capacity capable of delivering arelatively large current over a. sustained period. 'The principal objectof that invention is to provide such a cell and battery having a simpleconstruction which avoids the necessity of maintaining certain closetolerances and which is not susceptible to short-circuiting in themanner above described. More specifically stated, the object of thatinvention is to provide a dry cell having a large active anode area anda top which is covered by active elements of the cell which are capableof confining the mix to its proper location within the cell.

The object of the invention herein described and claimed is to provide amethod of making dry cells of the fiat type having a, covering sheetextending over the top thereof.

Other advantages and objects of the invention will become apparent .asthe description thereof proceeds.

In the accompanying drawing: a

Fig. l is a perspective view of a battery structure, partly broken away,embodying the invention; 7

Fig. 2 is a cross-sectional view of a portion of the battery of Fig. 1;

Fig. 3 is a plan view of the negative electrode assembly of the cellsshown in Figs. 1 and 2;

Fig. 4 illustrates, in perspective, a group of cells at one stage in theconstruction of the battery of Fig. l;

Figs. 5, 6 and '7 are perspective views, of alternative forms ofnegative electrode assemblies embodying the invention; and

Fig. 8 is a plan view of a further alternative form of negativeelectrode assembly.

The invention contemplates a cell having a negative electrode of sheetmetal which covers at least one broad surface of the fiat mix block andextends over the top of the mix block to form the top of the cell. Inall cases, an opening is provided in this top portion of the negativeelectrode, the separator element spans this opening, and the positiveterminal projects through the separator and opening at the top of thecell for connection with other cells of the battery or to the externalcircuit.

Referring to the drawing, battery I is composed of a sufiicient numberof cells 2 to furnish the voltage desired of the battery. Each cell 2contains a block 3 of mix having the known and usual composition, anegative electrode 4 of zinc, magnesium, or other suitable material, abibulous separator 5, also of known composition and func ti-cn, and asuitable positive terminal 6 which may be the usual carbon rod. Exceptfor the top, the cell so constituted is completely enclosed within apocket or envelope 1 of a suitable film material,

such as the product sold under the trade-mark Pliofilm, which isresistant to the action of the chemical substances of the cell fluidsand is electrically non-conductive As best shown in Figs. 1 and 2, thenegative electrode of this cell structure is U-shaped and is arranged inthe cell in inverted position so that the portion of the U-shapedelement which joins the two legs thereof, the bend of the U, forms thetop of the cell. The sides of this electrode are open; that is, the twoleg portions are substantially coextensive and coterminous with thebroad surfaces of the mix block 3, leaving the side edges thereofuncovered by the electrode. An opening 8 is provided in the top portionof the electrode exposing the portion of the bibulous separator element5 which underlies and spans the opening. Thus, the entire top of thecell is covered either by the separator element 5 alone or by a portionof the negative electrode in addition to the separator. Mix block 3 isnot exposed at the top of the cell.

7 The negative electrode assembly is illustrated in Fig. 3 in the formin which it appears before being bent to the shape in which it is usedin the cell- This assembly, which includes separator element 5, isformed from a rectangular blank of sheet metal. Opening 8 is punched atthe proper location at the middle of the blank, a lug 9 being left forthe purposes hereinafter described. The bibulous separator element,which may be a sheet of starch-coated paper, for example, is then laidupon the punched blank and the marginal portions 50. of the separatorturned back over the edges of the blank to overlap the marginal portionsof the blank on the side opposite to that covered by the separator. Thiselectrode assembly is then ready to be formed to the shape in which itwill be used in the cell wherein the separator element 5 will form alining for the electrode 4 to separate the same from the mix block 3.

In assembling the cell, the mix is inserted between the legs of theformed electrode. This may be done by directly extruding a slug of thematerial into the space between the legs of the electrode, or pre-formedblocks of mix may be inserted in any manner suited to productiontechniques. It is not necessary to observe the 'usual close tolerancesin carrying out this operation since the electrode assembly itselfestablishes the limit of insertion of the mix material into the cell.The carbon rod positive terminal 6 is then inserted by driving the rodthrough the separator 5 in the opening 8 of the negative electrode. Itis not necessary to provide a hole in the separator for this purposewhen the proper ma- "terial, such as paper of suitable strength, is usedas the separator element, the mix being sufliciently firm to support theseparator as the carbon is driven through. Insertion of the carbonterminal in this manner insures a close fit between the rod and theseparator so that no opening is left through which the mix may pass. Ifdesired, the carbon rods may be pointed to more readily pierce theseparator, but this is not cent cells. If the cells have been properlyspaced ture resistant coating material.

4 and oriented in carrying out this process, the string of cells soformed may be brought together in juxtaposed relationship by accordionfolding the string, as indicated in the drawing.

If desired, insertion of carbon rods 6 may be deferred until after thecells have been covered by the film material.

In fabricating the battery from the cells thus produced, the desirednumber of cells may be placed within a tray I0 and electricallyinterconnected by means of lugs 9 which may be bent to engage thepositive terminal of the adjacent cell. A suitable thermoplastic sealingmaterial ll may then be poured upon the tops of the cells and a finalmoisture-proof coating l2 may be applied, if desired, by dipping theentire sealed unit in microcrystalline' wax or other suitable mois-Suitable means, not shown, must, of course, have been provided forbringing out the battery terminals for connection to an externalcircuit.

It is desirable'that the cell elements be held together firmly toprovide good physical contact between mix, separator, and negativeelectrode. One function of tray I0 is to serve this purpose. The roundedtops of electrodes 4 permit any necessary flexing as the cells arebrought together under some pressure and inserted in the tray.

Alternatively, the juxtaposed cells may be held together by tape whichalso serves as a protective covering. With this arrangement, properlyapplied, the tray and top seal may be eliminated, a single dip inmicrocrystalline wax, bi-wax, or other suitable material sufiicing tocomplete and seal the battery unit.

Numerous alternative forms of negative electrode may be employed withoutdeparting from the principle of the invention. Examples of suchalternative forms are illustrated in Figs. 5-8.

In the negative electrode 4 illustrated in Fig, 5, an opening isprovided at each side of the electrode instead of a single opening inthe middle portion in the manner described above. This arrangement hasthe advantage of providing greater separation between terminal lug 9 andthe positive terminal of the cell, the eventual location of which isshown at 6 in dotted lines. This is particularly desirable in smallcells for the reason that the top sealing material may more readily andcompletely cover and seal the elements when so separated. As in the caseof the cells of Figs. 1 and 2, the entire top of the cell in which theform of electrode of Fig. 5 is employed will be covered by the-separatorelement and, in part,.by a portion of the negative electrode.

The electrode assembly illustrated in Fig. 6 is similar to that of Fig.1, the difference being the addition of a bottom flange l3 which extendsfrom the end of one leg of the electrode and is intended to underlie andsupport the mix block at the bottom of the cell, This flange increasesthe active area of the electrode and leaves only the two narrow sides ofthe mix block of the cell uncovered.

The electrode 4 of Fig. '7 consists of only one side and a top portion.This electrode, while simpler than that f the other embodiments of theinvention, provides the desired top covering for the mix block andthereby achieves the principal object of the invention.

Where it is desired to employ a separator ele- -ment which is of suchstrength that it is not possible to pierce it by the carbon rod in themanner above described, a small opening It may be punched in theseparator at the eventual location of the carbon terminal of the cell,as shown in the electrode assembly of Fig. 8.

From the examples given, many other modified forms of the invention willoccur to those skilled in the art and no attempt is made herein todescribe all possibilities.

Invention is claimed as follows:

1. The method of making a dry cell which comprises the steps of coveringwith contact engagement a surface, including the top surface, of a solidmix block with a bibulous separator element and thereafter inserting arod-like positive terminal at the top of the cell by forcing saidterminal lengthwise through the separator to rupture the same and intothe solid mix block.

2. The method of making a dry cell which comprises the steps of lining aU-shaped negative electrode with a sheet-form bibulous separatorelement, inserting a solid mix block between the legs of said electrodeinto contact engagement with said separator element, and thereafterinserting a rod-like positive terminal by moving said terminallengthwise through an opening in said electrode and through saidseparator element to rupture the same and into said solid mix block.

3. The method of making a dry cell which comprises the steps of lining aU-shaped negative electrode with a sheet-form bibulous separatorelement, inserting a solid mix block between the legs of said electrodeinto contact engagement with said separator element, applying anenvelope of film material to the assembly leaving that portion of theelectrode which connects the two legs thereof exposed, and'thereafterinserting a rodlike positive terminal into the cell by forcing saidterminal lengthwise through an opening in said electrode and throughsaid separator element to rupture the same and into said solid mixblock.

4. The method of making a dry cell which comprises assembling a solidmix block, negative electrode, and bibulous separator elements of thecell, enclosing the cell within an envelope of film material having anopening therein, and thereafter inserting a rod-like positive terminalelement into the cell by passing one end thereof through said opening inthe film material and a registering opening in said negative electrodeand piercing the separator element with said end of said terminalelement by forcing the latter continuing the lengthwise movement todrive the terminal element into the solid mix block of the cell.

5. In a method of making a dry battery, the steps of lining U-shapednegative electrodes with sheet-form bibulous separator elements,inserting a solid mix block between the legs of each said electrode intocontact engagement with said separator element, applying an envelope offilm material to each unit so assembled leaving that portion of theelectrode of each unit which connects the two legs thereof exposed,arranging the units in juxtaposed relation, and thereafter inserting arod-like positive terminal into each unit by forcing said terminalslengthwise through openings in said electrodes and through the separatorelements to rupture the same and into the solid mix blocks.

6. In the method of making a dry cell, the steps which comprise liningthe surface of a metal negative electrode having an opening therein witha sheet-form bibulous separator member in such manner that saidseparator member spans said opening, arranging a solid mix block incontact with the surface of said separator member remote from saidnegative electrode, and pushing a rod-like positive terminal lengthwisethrough said opening in said negative electrode, through said separatormember, rupturing the same, and into said solid mix block.

JOSEPH J. COLEMAN. MILTON E. WILKE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

